ATOUT Dep is the NH x deposition on land. ATOUT Export is the NH x transferred to
surrounding areas (mainly to ocean) through atmospheric circulation that advects
NH x away from China.
5.2.4 Datasets
We built multiple datasets to calculate N budget from 1980 to 2015 in China on both
a national and provincial scale. Data can be divided into two categories:
(i) socioeconomic information for China such as population, gross domestic product
(GDP), land use, fertilizer use, agricultural production, and energy consumption in
different sectors, all taken from the national data centre and FAO statistics, and
(ii) parameters and coefficients used for calculating N fluxes, both obtained from
peer-reviewed literature and field measurements. More detailed methods, data
sources, and the selection criteria applied and parameters and coefficients can be
found in Gu et al. (2015) and Zhang et al. (2017).
5.3 Nitrogen Budgets in China from 1980 to 2015
The overall N budget of China includes four major N inputs, Haber-Bosch N fixation
(HBNF), BNF, NO x emitted in fossil fuel combustion (NO x -FF), and import of
N-containing products, and four N outputs, N 2 emission, Nr transported outside
China via air and water, export of N containing products, and Nr accumulation
(Fig. 5.2). These items were all calculated on the subsystem level. For example, the
total BNF input to China was calculated as a sum of BNF input to different landbased subsystems including cropland, grassland, forest, and urban green land.
5.3.1 N Inputs
Total N input to China increased from 24.8 to 70.9 Tg N year
À1 from 1980 to 2015,
mostly due to an increase in HBNF from 12.6 to 48.5 Tg N year
À1 , and anthropogenic Nr amounted to 73% of total N input to China in 1980 and 85% in 2015. N
fertilizer use accounted 84% (in 1980) and 72% (in 2015) of total HBNF, and the rest
was for industrial N use. Lightning also creates Nr and input to terrestrial ecosystems, but we ignored this flux that is smaller than 0.1 Tg N year
À1 in China (Cui et al.
2013). With the exception of natural BNF, all of the other N inputs are well
constrained.
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B. Gu and X. Zhang
surrounding areas (mainly to ocean) through atmospheric circulation that advects
NH x away from China.
5.2.4 Datasets
We built multiple datasets to calculate N budget from 1980 to 2015 in China on both
a national and provincial scale. Data can be divided into two categories:
(i) socioeconomic information for China such as population, gross domestic product
(GDP), land use, fertilizer use, agricultural production, and energy consumption in
different sectors, all taken from the national data centre and FAO statistics, and
(ii) parameters and coefficients used for calculating N fluxes, both obtained from
peer-reviewed literature and field measurements. More detailed methods, data
sources, and the selection criteria applied and parameters and coefficients can be
found in Gu et al. (2015) and Zhang et al. (2017).
5.3 Nitrogen Budgets in China from 1980 to 2015
The overall N budget of China includes four major N inputs, Haber-Bosch N fixation
(HBNF), BNF, NO x emitted in fossil fuel combustion (NO x -FF), and import of
N-containing products, and four N outputs, N 2 emission, Nr transported outside
China via air and water, export of N containing products, and Nr accumulation
(Fig. 5.2). These items were all calculated on the subsystem level. For example, the
total BNF input to China was calculated as a sum of BNF input to different landbased subsystems including cropland, grassland, forest, and urban green land.
5.3.1 N Inputs
Total N input to China increased from 24.8 to 70.9 Tg N year
À1 from 1980 to 2015,
mostly due to an increase in HBNF from 12.6 to 48.5 Tg N year
À1 , and anthropogenic Nr amounted to 73% of total N input to China in 1980 and 85% in 2015. N
fertilizer use accounted 84% (in 1980) and 72% (in 2015) of total HBNF, and the rest
was for industrial N use. Lightning also creates Nr and input to terrestrial ecosystems, but we ignored this flux that is smaller than 0.1 Tg N year
À1 in China (Cui et al.
2013). With the exception of natural BNF, all of the other N inputs are well
constrained.
92
B. Gu and X. Zhang